1. Field of the Invention
This invention relates in general to certain new and useful improvements in vehicle wheel inserts and lug nut assemblies thereof, and more particularly, to such vehicle wheel inserts which are in cooperative relationship with lug nuts in non-ferrous wheels for ensuring a precise and accurate tightening of the wheel against the vehicle hub without any damage to the vehicle wheel and which precludes unauthorized vibrational unwinding of the lug nuts.
2. Brief Description of the Prior Art
In recent years, automobile manufacturers have resorted to the production of non-ferrous wheels for motor vehicles and particularly, wheels made of aluminum and magnesium. In addition, wheels which are made of non-ferrous materials are frequently offered in the automotive aftermarket or so-called "secondary market" for purposes of customizing a vehicle. As a result of their light weight and attractive appearance, non-ferrous wheels have thereby become popularized. Accordingly, many automotive enthusiasts will therefore substitute these non-ferrous wheels for the conventionally provided steel vehicle wheel.
One of the major problems with the use of non-ferrous wheels, such as aluminum wheels, is the fact that the lug nuts have a tendency to become loose from vibrational effects and as a result of wear resulting from the steel lug nut rubbing against the softer aluminum seat during wheel rotation. The flexing of a wheel mounting stud normally occurs due to vibrations resulting from road conditions, wheel braking, sudden acceleration with resultant movement between the lug nut and the soft aluminum seat. This results in significant wear on the aluminum seat and also causes the corners of the hexagonal portion of the lug nut to literally dig into the soft aluminum seat.
Steel inserts have been used in the stud-receiving openings of non-ferrous wheels in order to eliminate some of the deformation of the aluminum or other non-ferrous wheel when a lug nut is tightened against the wheel. These inserts are all provided with integral skirts and the skirts are provided with a knurled surface on the exterior wall of the cylindrically shaped skirt. In this way, the conical section of the insert fits within the conically shaped portion of the stud-receiving opening and the cylindrically shaped skirt fits within the cylindrically shaped portion of the stud-receiving opening and locks the insert in this stud-receiving opening by virtue of the frictional fit of the knurls against the wall of the stud-receiving opening.
One of the principal problems with the use of this type of insert is the fact that it is necessary to literally machine the knurled surface or other serrations on the exterior wall of the skirt. Moreover, these inserts must be forged from steel and cannot be stamped from thin sheet metal, due to the need of the skirt and particularly, the knurling on the exterior surface thereof. The knurling on the exterior wall of the skirt is important to overcome differences in tolerance. If the skirt is not precisely sized to fit within the cylindrically shaped portion of the stud-receiving opening, then the insert can literally fall out of the stud-receiving opening during shipment or handling of the wheel. Even more importantly, the steel insert can be readily dislodged from the stud-receiving opening during the mounting of the wheel and interfere with installation of the wheel. If the wheel were actually installed without the insert, the lug nut would neither align the wheel properly nor provide sufficient seating area and this could become a significant road hazard.
Inasmuch as these prior art inserts have been formed of forged steel, they weigh as much as four to six times the amount of equivalent stamped sheet metal inserts. Due to the fact that there is a substantial decrease in weight by using a stamped sheet metal insert, there is a far less possibility of wheel imbalance occurring.
In the case of standard OEM steel wheels, a torsion ring is used. The steel wheels are frequently constructed so that a portion of the wheel surrounding the stud-receiving opening actually functions as a type of torsion ring. This creates a Belleville spring effect. Thus, when a lug nut is tightened against a steel wheel, the wheel surface around the lug nut will actually deflect slightly, causing a spring loading on the lug nut. This spring loading or Belleville effect actually places the lug nut under compressive force loading on the vehicle wheel stud and prevents the lug nut from vibrating loose on the vehicle wheel stud.
There have been several attempts to duplicate the torsion ring effect of steel wheels in the manufacture of aluminum and other non-ferrous wheels. However, these attempts have not met with success, particularly in the case of aluminum wheels. Aluminum, in particular, is not a desirable spring material. Furthermore, the thickness of the aluminum wheel in the lug nut mounting area, that is, around the stud-receiving holes, is actually four times thicker then in a corresponding steel wheel. As a result, the aluminum wheel manufacturers were not able to obtain any effective Belleville spring effect.
Another one of the problems which arise in the case of non-ferrous wheels is the problem of accurately centering the wheel on the studs projecting outwardly from the vehicle hub so that each stud is concentrically located at the exact diametral center line of the stud-receiving hole in the vehicle wheel. When the vehicle wheel is initially placed onto the vehicle, the weight of the wheel effectively rests on one or more studs and particularly, the uppermost studs. When the lug nut is tightened against the conical seat of the vehicle wheel, it actually causes a raising of the wheel in an effort to center the wheel with respect to the vehicle stud. The forcing of the steel lug nut against the soft aluminum conically shaped seat literally destroys the accuracy of this aluminum seat.
In order to improve the aesthetics of the wheel mounting arrangement, many users of non-ferrous wheels will employ chrome plated lug nuts for securing the wheel on the vehicle studs. However, when a chrome plated lug nut having an exterior conically shaped surface is tightened onto a conically shaped aluminum surface, the chrome on the lug nut will gall the aluminum seating surface. This galling of the aluminum seat effectively destroys the seat and particularly, the ability to accurately center the wheel with respect to the studs. This problem has been observed by many major automotive manufacturers and, as a result, these manufacturers have written specifications to allow for some galling of the aluminum wheel. Other automotive vehicle manufacturers prohibit the use of, or strongly recommend against the use of chrome plated lug nuts on aluminum and other non-ferrous wheels.
Wheel inserts which are presently used on aluminum wheels are made on headers and screw machines. The header used to manufacture an insert is a very expensive piece of equipment with a cost easily exceeding $1,000,000.00. In addition, the initial tooling costs alone are $30,000.00. It would be necessary to utilize a header for producing these steel inserts in order to produce the inserts at a cost which is not prohibitive.
The applicant has taught of the use of inserts in vehicle wheel nut assemblies for securing non-ferrous wheels to the hub of a vehicle as, for example, in U.S. Pat. No. 4,898,429 dated Feb. 6, 1990 for "Vehicle Wheel Assembly." However, the inserts taught in this U.S. patent all required the use of a cylindrically shaped skirt portion surrounding the conical seat. Moreover, this invention taught the use of lug nuts, each having a body section with tool-engaging walls and a skirt located on and extending axially from the tool engaging walls of the lug nuts. However, in accordance with the invention in this U.S. Pat. No. 4,898,429, and due to the fact that the lug nuts were of a different construction, a means to retain the insert in the stud-receiving opening was not addressed.
Others have proposed the use of inserts in vehicle wheels as, for example, in U.S. Pat. No. 3,329,468 dated Jul. 4, 1967 for Wheel Structure, U.S. Pat. No. 3,811,737, dated May 21, 1974 for a Reinforced Resin Wheel, U.S. Pat. No. 4,679,860 dated Jul. 14, 1987 for a Wheel Assembly For Vehicle, and U.S. Pat. No. 3,988,038 dated Oct. 26, 1976 for a Universal Wheel System. Other prior art wheel inserts have been taught in Offenlegungsschrift No. 2026332 dated Dec. 17, 1970 and Japanese Patent No. 60-197101 for Built-Up Wheel for Vehicles, by Honda Giken Nogyokk.
There has been a need for some arrangement, including a steel insert which would allow the use of a steel lug nut for securing a non-ferrous wheel to the wheel hub of a vehicle. The use of this insert would provide a torsion ring effect for an aluminum wheel and thereby prevent the lug nuts from becoming loose as a result of vibrational effects on the wheel. In like manner, it would be desirable to use some type of steel insert to eliminate the destruction of the aluminum seat surrounding the wheel stud when a steel lug nut is tightened against the aluminum wheel. It is also desirable to allow the use of plated lug nuts, e.g., chrome plated lug nuts for securing the wheel to a wheel hub of a vehicle.